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Dec 21st 2020

Does Pluto Have Storms?

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Once thought to orbit alone as the most distant outpost of the solar system, Pluto is now known to be the closest and — one of the largest — members of a vast outer system far beyond the eight major planets, extending out to an appreciable fraction of a light-year from the sun.

Pluto itself has also turned out to be a far more complicated world than once imagined. It has its own system of five moons, the largest of them half its own size. It has an atmosphere. But does Pluto have storms?

As with most questions on the frontiers of science, the answer is uncertain. But chances are good that it does at least have snow — evoking a classic bit of science fiction and also pointing toward an even more surprising discovery: Pluto may have an underground ocean.

A Blizzard on Pluto

For fans of Golden Age science fiction, rugged weather on Pluto has a bit of a history. A 1950s novel by classic science fiction writer Robert Heinlein, “Have Spacesuit, Will Travel,” featured its teenage protagonist making his way to safety through a Plutonian blizzard.

Little was known about Pluto at that time, and the book’s version of Pluto had little in common with what modern investigations had revealed about it, including the New Horizons spacecraft that flew past Pluto in 2015.

But one thing astronomers did know about Pluto in the 1950s was that it had an eccentric orbit, ranging between about 30 and 50 times Earth’s distance from the sun. Author Heinlein guessed — correctly, as it turns out — that Pluto would have an atmosphere and that its orbit could produce dramatic seasonal changes in weather in the course of the long (248 Earth years) Plutonian year.

Your Pluto WeatherCast

For an up-to-date report on the weather on Pluto, we can turn to none other than the National Weather Service. The first thing to know is that Pluto is incredibly cold, with a surface temperature ranging between about –370 and –400 degrees Fahrenheit.

Considering its distance from the sun, Pluto’s nippy weather is not a surprise. But according to Space.com, it is even colder than astronomers expected. The reason, investigators now suspect, is that a layer of haze forms high in Pluto’s thin atmosphere, absorbing much of the little sunlight that reaches Pluto. Thus, under its blanket of haze, the surface is even colder than it would otherwise be.

But does Pluto have storms? We are not yet sure, but we do know that it has some form of snow.

A World With Snow

As Scientific American reports, Pluto is one of the handful of solar system bodies that seems to have some form of snow; the others include Titan, Io, Mars and, of course, Earth. But on Pluto, uniquely, almost the entire atmosphere may fall as snow.

In Plutonian winter, most of the atmosphere condenses to solid material on the surface. In fairness, we don’t know whether these frozen gasses fall as grains or snowflakes or simply condense on the surface like rime frost.

Likewise, we don’t really know yet whether Pluto’s atmospheric changes and freeze-out are accompanied by fierce winds — in short, a blizzard — or if it more nearly resembles a light snowfall under a bitter cold haze.

And an Ocean World?

Pluto’s most conspicuous surface feature, a heart-shaped Sputnik Planitia, is made up largely of nitrogen ice, some of which melts or sublimates into the atmosphere during Plutonian summer, while some remains frozen year-round.

But according to a separate report at Space.com, Sputnik Planitia also contains water ice. Characteristics of the region suggest that it was formed by an ancient impact and suggest that the water ice welled up from below after the impact. This in turn suggests that, beneath its frigid surface, Pluto may still have an ocean of slushy water, prevented from freezing by an insulating layer of “gas hydrates.” The subsurface ocean is also kept warm by gravitational flexing between Pluto and its large moon Charon.

So, does Pluto have storms? Perhaps it depends on how exactly you define a storm. Whether or not it ever has howling blizzards, it certainly has some rugged weather. Blizzard or no, a temperature of –390 Fahrenheit and snowing is weather you don’t want to mess with.

But, for the properly prepared, what an unexpected, fascinating world!

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